Electrical control circuit



J1me 3Q, 1936. H. H. GEFFCKEN ET AL, 2,@459769 ELECTRICAL CONTROLCIRCUIT Filed May 17, 1929 a M. @fza Dww la g Patented June 30, .1936 pa 2,1)455'69 umrso STA-res. PATENT DFFI'CET;

Heinrich Hermann Geilcken and Hans Rudolf Richter, Leipzig, Germany,assignors, by mesne assignments, to Radio Corporation of America, NewYork, N. Y" a corporation of Delaware Application May 17, 1929, SerialNo. 363,761

In Germany May 31, 1928 tillaims. (c1. 250-21) This invention relates toan electric control an amplifier with a limiting or critical value, oncircuit, more particularly to an amplifying circuit exceeding which a.sudden change 01 current adapted for controlling a mechanical relay ortakesplace insuring reliable operation the similar device by a weakcurrent or potential mechanical relay connected with the amplifier.

5 impulse. The invention has special use in segre- In apparatusheretofore known using ordinary 5 gating or sorting systems chosenherein for illusamplifiers in connection with mechanical relays, trationalthough not limited thereto.- the degree of differentiation of thebodies being It is known that the tuning of a resonant cirtested isdetermined by the limiting response cuit may be modified by the magneticor dielecvalue or sensitivity of the mechanical relay.

tric properties of a body by introducing the body With an amplifierconstructed and arranged ac- 10 into the electric field of a condenserorinto the cording to the present invention on the other 'nagnetic fieldof a self induction coil inserted in hand, the sensitivity is determinedby the limitthe resonant circuit. The extent to which the ing orcritical value of the amplifier. Moreover, tuning of the circuit ismodified depends on the in thermionic valve relays such a limiting orproperties of the body in question. With the ascritical value can befixed in a much more exact it; sistance of well known devices such aswith the and constant manner and is much less aflected aid of aresonance arrangement, it is possible, by outside influences such asmoisture, vibrations with the use of amplifiers, to control or operateand the like, than an ordinary electromagnetic relays whenever thechange in the tuning of the relay.

resonant circuit, produced by thebody to be A further advantage of thepresent invention 20 tested, exceeds a given limit. is the possibilityof using in most cases a much It is further known that it is possible toprosmaller number of thermionic valves. duce a tightening of thecoupling between two In order that the invention may be clearly coils bymeans of magnetic bodies, by introducing understood and readily carriedinto effect, the

5 the latter between the coils in question. When some will now bedescribed more fully with referan alternating current passes throughonecoil, ence to the accompanying drawing, in which:- an alternatingcurrent will also be induced in the Figure 1 is a diagrammatic view of aseparating second coil owing to the coupling produced by device in whichthe invention may be advantathe body to be tested, and with the aid 01'well geously used, and

0 known amplifying devices it is possible to operate Figure 2illustrates by way of example the con- 0 a mechanical relay by means ofthe induced altrol and amplifying circuit according to the internatingcurrent whenever the coupling provention. duced by the body to be testedexceeds a prede- Referring to Figure 1, the pieces of mineral i terminedlimit. to be separated, some of which may contain mag- Finally, it isknown that a body which is netic material and are to be separated fromthe 5 brightly illuminated by a lamp and brought in others, fall throughthe slideway 2 into the hopfront of a device sensitive to light such asa. per 3 and from the latter through the coil 4 photoelectric device,selenium cell or the like, into the separating mechanism. The separatingcauses an electric current to be produced by the mechanism consists ofan electrically operated photoelectric device, the strength of whichvaries flap valve 5 which is either in the position shown 40 inproportion to the brightness or the color oi the in the drawing in fulllines or in the position body in question. With the aid of amplifiers itindicated by dotted lines, and serves to guide the is possible tooperate mechanical relays by means pieces of material I into theslideway 5 o h of such an electric current whenever the brightslideway 1respectively. The coil 4 is part 01' the ness of the body tested isgreater or smaller than electric device 8 controlling theelectromagnetic 45 a given value. relay 9. The flap valve 5 is normallyin the posi- All these well known phenomena have already tion shown inthe drawing in full lines, so that been utilized for obtaining anautomatic separathe descending pieces of material are guided into tionof materials. In individual cases they have the slideway 6. As soonhowever as one of. the

also been used for separating rocky minerals into pieces I containssuflicient quantities of mag- 50 difierent groups according to theirproportion oi. netite, it will act on the coil 4, and there will be orecontent. produced in the device 8 an electric efiect caus- The presentinvention which may be applied ing response of the relay 9. As soon asthe relay with advantage in any of the systems o1 the 9 is operated, theflap 5 will be thrown over into character indicated, consists in theprovision of the position shown in dotted lines, and the piece 55 handplate of the condenser 2 I.

of material in question willbe guided into the slideway I. In thismanner all the pieces which do not contain any magnetite, or in whichthe proportion of magnetite is below a certain limiting value, will beguided into the slideway 0, while the pieces containing a proportion ofmagnetite above said value will follow the slideway I and will thus beseparated from the pieces having a lower magnetite proportion.

Figure 1 is intended merely to be illustrative of the purpose and usesto which the present invention is to be applied. The invention itselfrelates to a new arrangement and construction of the electric device 8,shown in Figure 2.

Referring to Figure 2, the electric device 0 comprises two coils IO andII and a condenser I2 connected in series with the coil 4. A thermionicvalve I3 is arranged in one of the usual oscillating circuit connectionsto produce undamped oscillations applied through the coil It to theoscillation circuit comprised of the coils 6, Illand I I and thecondenser I2. This oscillation circuit is tuned in such a manner thatits wave length is somewhat less than that of the undamped oscillationsin the generator coil It. When a magnetic body enters the coil 4, theself induction of the latter will be increased; consequently theoscillation circuit 4, I0, II, I2 will come into resonance with thefrequency of the valve generator I3, I4 and an oscillating current willbegin to flow in the said circuit. The oscillating current is appliedthrough the coil I5 to the grid of a thermionic valve I'l arranged toact as a detector by the provision of a grid leak-grid condensercombination I6 arranged in a known manner. Since the valve I1 is inseries with the resistance I8 and since the action of the oscillationson the detector tube I1 increases the internal resistance of the tube,the potential drop across the tube will increase. Instead however ofamplifying this increase of potential in the usual manner by means ofseveral thermionic valves to an extent as to enable it to operate orcontrol a relay which then responds or does not respond according to themagnitude of this potential, the increase of voltage is appliedaccording to the present invention to a discharge tube relay constructedto have a critical value, 1. e. a sudden change of its output currenttakes place if the said value is exceeded, whereby an electromagneticrelay may be operated in a reliable manner. The relay circuit and itsfunction will now be described.

The glow tube I9, resistance 20 and the translating device or relay 9are connected in series across the current source 22. The condenser 2Iis connected to the junction point between the glow tube I9 and seriesimpedance 20. The detector tube H in series with the resistance I 8 isalso connected across the source 22 and forms a voltage divider circuitfor producing varying positive control impulses to be applied to theleft As is understood, any other input circuit may be arranged to supplya positive control impulse. In the example as shown, if oscillatingcurrents are applied to the grid of the tube II, a choking or blockingeffect of the tube takes place causing an increased tube impedanceresulting in a positive potential rise at the junction point between theanode oi. tube I1 and the resistance I8. As a result, the left handplate of condenser 2| will temporarily become positive when acontrolling impulse occurs, such as caused by an object I (see Fig. 1)con-- taining a predetermined proportion of magnetizable materialpassing through the coil 4 as described hereinbei'ore. The positivepotential at the left hand plate of condenser 2| causes a correspondingnegative potential to be set up at the right hand plate of thecondenser; or in other words, electrons will accumulate at the righthand plate. The latter are drawn from the space current and the upperelectrode of the glow tube, thus temporarily increasing the potential atthe upper electrode to a degree sufllcient to cause initiation of a glowdischarge through the tube I9. After the discharge through the tube hasbeen started, the condenser 2| will at once be discharged through thetube acting as a leak path and a renewed discharge may be started by anew control impulse, such as by a second object containing sufllcientmagnetizable material ail'ecting the input circuit. The impedance 20 ischosen in such a manner that the potential at the junction under normalconditions has a definite value below the sparking potential 01 the tubeis so that a discharge is effected only by a control impulse ofpredetermined minimum intensity. As the amount of the change ofpotential produced depends on the proportion of magnetite in the pieceof material I under testwhich is acting upon the coil as, the questionas to whether the piece I is guided into theslideway I or not on thebasis oi its contents of magnetite, is determined therefore by theelectric critical value which represents the ignition voltage of theglow discharge tube I. As this "electric critical value" is 0! coursedefined much more accurately than, and cannot be aiiected by anyexterior influences (moisture, vibrations, rust and the like) to thesame extent as the mechanical limiting responsive value at which anelectromagnetic relay becomes operative, a device according to thepresent invention will work in a much more accurate and consistentmanner than devices heretofore known for this purpose.

Many modifications so far as actual details are concerned may of coursebe made in carrying out the present invention within the limits of itsessential principle. Thus, the glow discharge tube Il may be replaced bya thermionic valve arranged in a condition or sudden discontinuity toprovide similar electric trigger action to a gaseous glow tube asdescribed. Further, in place of the critical voltage there could also beused critical conditions or limits as regards frequency or phase such asare encountered in coupled oscillation circuits.

What we claim and desire to secure by Letters Patent 0! the UnitedStates is:-

1. In combination, an electric gas discharge device having a pair ofelectrodes; an impedance and a source of current; said gas dischargedevice, said impedance and said source being in series; the potential atthe junction point between said gas discharge device and said impedancebeing normally insuflicient to eflect an ionic discharge through saiddevice; an electrical condenser having one plate thereot connected tosaid junction point: means for applying controlling potential impulsesoi momentary duration and of predetermined intensity to the remainingplate of said condenser to vary the potential of said junction point tosuch an extent as to eilect a discharge through said device; atranslating device; and means for operating said translating device fromthe output of said gas discharge device.

2. In combination, an electric gas discharge tube having a pair oi.electrodes therein; an impedance; a translating device and a source ofcurrent; said discharge tube, said impedance, said translating deviceand said source being in series with the positive pole of said sourcebeing connected to said impedance; the potential at said junction pointbeing normally too low to cause an ionic discharge through said tube; anelectric condenser having one plate thereof connected to said junctionpoint; means for applying a positive control potential impulse ofmomentary duration and of predetermined intensity to the remaining plateof said condenser to produce a positive potential rise at said junctionpoint to effect a discharge through said tube and operate saidtranslating device.

3. In a control circuit, a discharge device adapted to undergo a suddendiscontinuous change of impedance when subjected to a predeterminedcritical terminal potential; an impedance and a source of current, saiddevice, said impedance and said source forming substantially a seriescircuit; the potential at the junction point between said device andsaid impedance being normally below said critical potential; an electriccondenser having one plate thereof connected to said junction point;means for applying a positive controlling potential impulse to theremaining plate of said condenser to change the potential at saidjunction point to a value equal to or beyond said critical potential toinitiate the change oi impedance of said device.

4. In a control circuit, an ionic device having a pair of electrodes; animpedance and a source oi. current, said device, said impedance and saidsource being connected to form substantially a series circuit with saidimpedance connected to the positive pole of said source; the potentialat the junction point between said device and said impedance beingnormally close to the critical point at which an ionic discharge isproduced through said device; an electrical condenser having one platethereof connected to said junction point; and means for applying apositive control potential impulse to the remaining plate of saidcondenser to increase the potential at said junction point and initiatea discharge through said 20 device.

HEINRICH HERMANN GEFFCEEN. HANS RUDOLF RICHTER.

